Various types of lubricant compositions have been used in metal working as, for example, in cold rolling processes involving ferrous metals. For the most part, however, such compositions provide inadequate lubrication or cause objectionable surface discoloration or imperfection. In many instances, they are ineffective in preventing the formation of rust during processing.
Rolling oils for metal fabrication historically have been based on vegetable and animal fatty acids. These fatty acids are often diluted with mineral oil. The primary purpose of these oils is to enhance the surface appearance of the finished metal product with anti-wear and lubrication being a necessary, but secondary, requirement. Although the addition of palm oils, for example, reduces the problems associated with the use of the base oil alone, there is still evidence of surface transfer of metals from the sheet to the rolls. Although this can lead to accelerated wear, the worst problem is the appearance of the final rolled sheet. If the final product contains chips or bumps and surface defects, it is often sent back to the furnace. In view of studies that have been made, palmitic acid provides lubricity but does not provide extreme pressure properties under the high loads produced by asperities on a microscopic level. In accordance with the invention, it has been found that the addition of a small amount of a sulfur-containing additive improves the extreme pressure properties of the lubricating oil.
Accordingly, an object of this invention is to provide improved additives for lubricating compositions.
Another object of this invention is to provide improved lubricating compositions utilizing the additives of the invention.
A further object of this invention is to provide an additive for oil-based industrial lubricants to improve the surface appearance of the work.
A further object of this invention is to provide rolling oils exhibiting reduced wear and improved surface appearance of the work.
Other objects, aspects, as well as the several advantages of the invention, will be apparent to those skilled in the art upon reading the specification and the appended claims.